|My two cents:|
"So if someone at my work was emailing\browsing\looking at unsavoury sites\or simply slacking on the job managment could if they want see him through a network even without the user knowing.."
It's not necessary to "see" someones desktop. All the websites you visit can (and likely are) logged and the logs can be viewed at any time by an authorized admin. Email itself can also be viewed, if need be, by the email admin. It's not at all hard to setup your email server to keep copies of all email.
It's not necessary to install key logging software or spyware like something that allows you to "see" what the user is doing on their desktop.
Most companies, like the one where I work, do the above. If, like our company, you're not allowed to play games at work (makes sense, you're there to work, play at home on your own PC) then they simply don't install the games.....period.
As for the laptop question. If you're running a linux based laptop, you could spoof your MAC in about 3 seconds flat to any MAC address you wanted to put in. The only thing 'authorities' could find out for sure is where you connected (ie: from what provider) depending on the hackers knowledge and abilities. This is why people who hack and deal in garbage like childporn 'wardrive' looking for unsecured wireless networks. The only defense, especially for home users is to secure your WLAN with encryption and any/all other means available to you making it as hard as possible for anyone to get into and use your WLAN. A hacker will simply go on by a secured WLAN and not bother attempting to hack it as they know in a matter of minutes (if not seconds) they'll find one that's not secured.
A good analagy is break and enter artists. If lights are on or they hear a dog bark when they knock on your door (no lights), they simply move along and look for a home that's dark with no dog. Path of least resistance right. The same applies to WLAN's.